Optometer of the scheiner system.



W. THORNER.

OPTOMETER OF THE SCHEINER SYSTEM.

APPLICATION FILED MAR. 10, 1915.

1,235, 1 70. Patented July 31, 1917.

2 SHEETS--SHEET ifz'fizmsm- WgZW/EZK Q a g fizz" [/2617 wr uoam.OPTOMETER OF THE SCHEINER SYSTEM.

APPLICATION FILED MAR. 10' l9i5.

Patented J uly 31, 1917,

2 SHEETSSHEET 2- 'Fzyy. 3.

Java/z Z01".- Wadi 140% 1; Mr/y WALTHER THORNER, OF BERLIN, GERMANY.

OPTOMETER OF THE SCHEINER SYSTEM.

Specification of Letters Patent.

Patented July 31, 1917.

Application filed March 10, 1915. Serial No. 13,475.

.have invented certain new and useful Imgrovements in Optometers of theScheiner ystem, of which the following is a specification.

My invention relates to optometers or instruments used in the art ofophthalmoscopy. In the optometers of the Scheiner system two narrowapertures are placed before the pupil of the eye and through theseapertures a small object such as the point of a needle is viewed, thisobject appearing single only in the case where the eye is exactlyadjusted upon it, while inall other cases it will appear double.Scheiners optometers are little adapted for practical use for the reasonthat in order not to let the image appear too diffuse, the observationapertures have to be exceedingly narrow. Now it is very difficult indeedto make apertures which are sufliciently narrow, and such apertures willeasily become stopped up and will darken the image to a great extent.

The present invention does away with this drawback by replacing theapertures to be placed before the eye by optically'real images of suchapertures. The real apertures must lie in a plane conjugated to thepupil and must be reproduced in the plane of the pupil by some opticalmeans such as a convex lens. Such an arrangement offers the furtheradvantage of allowing to transfer the real image of the two aperturesinto the plane of the pupil itself and to obtain thereby a greater rangeof view, while, if real apertures are used as is the case in Scheinersdevice, these real apertures can be placed only outside the eye, therange of view being greatly narrowed in this case. Instead of producingin the pupil images of real apertures, it is simpler to use thread orpoint shaped sources of li ht and to project these sources of lightwithin the plane of the pupil. In this case the thread shaped source oflight itself replaces the aperture as no other light besides the lightemitted by the thread shaped source of light can reach the eye and thesame eflect is obtained as if a. slit was placed in the placeof thethread -shaped source of light.

The measuring of the ametropia by aid of this instrument is effected bydisplacing an object of fixation, preferably a narrow slit in thedirection of the optical axis until the slit does not appear double anymore but single. If it is desired to obtain the arrangement well knownin optometers viz. that an equal displacement of the object of fixationcorresponds to each dioptric ametropia, the pupil of the eye must beplaced in the focus of that convex lens which serves for the observationof the object of fixation and at the same time for the reproduction ofthe sources of light within the pupil. In order to distinguish thedouble images, they may be illuminated in a well known manner withlights of difl'erent color.

The principle described above can be realized in a still simpler mannerby employin only a single source of light. To this en the object offixation is partly covered with a body deflecting the rays for instancewith a prism, so that the rays passing through the uncovered part andthe rays paming through the covered part of the object of fixation aredirected to different parts of the pupil. Instead of leaving part of theobject of fixation uncovered, different parts of it may be covered'withdeflecting bodies (prisms or the like) placed in such a manner as todeflect the rays to different sides of the pupil. In order to preventthe instrument from assuming an undue length, the source of light ispreferably transferred by means of a telesystem into apparent infinityand this image lying in the infinite space is reproduced in the plane ofthe pupil by the convex lens serving for the observation of the objectof fixation.

It is further advantageous to have a means for excluding theaccommodation with certainty. This is obtained, if the observer looksupon objects placed afar and sees the object of fixation apparentlyprojected upon these objects. In order to realize this the object offixation is observed by reflection in a pane of glass while the observeris looking at objects placed afar through the same pane. The wholeinstrument is preferably arranged vertically. In order to avoid the paneof glass reflecting double images, it is advisable to employ a pane of athickness which will cause the images of the object produced by its rearsurface to fall entirely outside the aperture of observation.

If the source of light used is a thread shaped electric glow lamp, theolojeet of fixation must consist of a slit parallel to the filament ofthe lamp as if placed at a right angle to the filament it would appearbroadened. If a point shaped source of light is used, the object offixation may have any shape, such as a cross or the like. In this lattercase the instrument may also be employed for ascertaining astigmatism.For the line of the cross at right angles to the refracting edge of theprisms will appear single only in the principal meridians, whereas inall the other meridians it will appear refracted. Instead of employing across, a slit shaped object of fixation may he rotatably arranged.

In the drawings afixed to this specification the preferred form of myinvention is represented.

Figure 3. shows diagrammatically the path of the rays in the case of twoseparate sources of light heing snip-l 'yed.

Fig.2 shows the way in which mages wiii he displaced on the chi on beingdis laced.

shaped source said diaphragms. i is the image of f, The unilluminated pasponds to the optical I mbetween the two dine can be displaced in the iI 1 cal axis on a scale graduated in c op Fig. 2 shows the slit sappears to the eye in dinerent refractions in case that it is placed inthe position zero, that is in the plane of the the slit 6 is coveredwith a red F e a slit with a green glass, the pa 1 contains green imagered image.

pin a Then a red line and a half of the slit a? is green glass and thered glass then one I red lines will be seen a lhen ca shows the p"iornenon of hypermetropia, (i one one teinmetropia and the one in thecase myopia.

With reference to Fig. 8, IE. the base of the optometer carrying lievertical 2t 3 is the convex lens fastens to end of the tube. A sleeve iis arranged within tube 2..

shaped source of light, 6 is a concave lens, a convex lens. 8 is theobject of fixation having a slit or any other suitable perforation andcovered with two crossed prisms 9 and 10. The parts 5, 6, 7, 8, 9, and10 are relatively stationary within sleeve 4. Sleeve 4 can be moved upand down Within the tube 2 and can be turned around its longitudinalaxis if it is desired to ascertain astigmatism. 11 is the observers eye,12 and 13 are the two real images of the source of light 5 reproduced inthe pupil of entrance. iiis the transparent pane of glass reflecting therays entering the eye at its front surface. The

i 4. 1 7 T In an optoineter or tea tem, in ocrnhination, narrowly co edsources of lignt and means for reproiing images of narrowly confinedsources of light in the plane of the pupil of the e e.

2. ln optometer of the Scheiner system, in combination, narrow lightbodies and means for reproducing images of narrow light bodies in theplane oi the pupil of eye.

In an cntometer ten, cc source of l reduces.

the sys= non, a narrowly confined and means "for repro 4' 3 rages OiSEAS narrowl 'ir ht in "h Q 1 Y r a es 01 sale narrow ligne oody 13 nopiano or the pupil oi the eye.

5. in an optometer oi the Scheiner systern, in combination, a narrowlyconfined source of li ht, means for reproducing re duced images or" saidsource of light in the plane of the pupil, an object of iaesaao meanscovering said object and adapted to deflect the rays of light emanatingfrom said source of light to different parts of the pupil.

6. In an optometer of the Scheiner system, in combination, a narrowlyconfined source of light, means for reproducing reduced images of saidsource of light in the plane of the pupil, an object of fixation, aplurality of bodies covering said object and adapted to deflect the raysof light emanating from said source of light to different parts of thepupil, an optical tale-system for apparently reproducing said source oflight in the infinity and means for displacing said tele-system, saidobject of fixation and said deflecting bodies all together relatively.to the means of reproduction of the object of fixation.

7. In an optometer of the Scheine'r system, in combination, a narrowlyconfined source of light, means for reproducing reduced images of saidsource of light in the plane of the pupil, an object of fixation, aplurality of bodies covering said object and adapted to deflect the raysof light emanating from said source of light to different parts of thepupil, an optical tele-system for apparently reproducing said source ofli ht in the in finity, means for displacing said tele-system,

said object of fixation and said defl bodies all together relatively tothe means of reproduction of the object of fixation and a transparentmirror placed obliquely in the plane of intersection of the light raysand the pupil axis.

8. In an optometer of the S'cheiner sys term, in combination, avertically disposed tube, a sleeve within said tube, an'electric glowlamp in the lower end of said sleeve, a point shaped filament in saidlamp, a telesystem, a pair of crossed prisms and a diaphragm in saidsleeve above said prisms, means for turning and vertically displacingsaid sleeve and the parts fixed in it within said tube, a convex lens inthe upper end of said tube, a transparent mirror disposed at an angle of45 a ove said convex lens and an aperture for observation above the lensand in the plane of intersection of the rays of light of the lamp andthe transparent mirror.

In testimony whereof I aifix my signature in presence of two witnesses.

DR. WALTHER THORNER.

Witnesses HENRY Hasrna, WOLDEMAR HAUM'.

